INFLUENCE OF A LONG-TERM ZINC-DEFICIENT DIET ON RAT PLATELET-FUNCTIONAND FATTY-ACID COMPOSITION

A reduced zinc intake is associated with numerous abnormalities and, i n particular, with hemostasis dysfunction. In this report, we studied the effects of a long-term dietary zinc restriction on platelet functi on. Three groups of rats were analyzed: a zinc-deficient group (ZD) an d two zinc-adequate fed groups, one pair-fed (PF) and one ad libitum f ed (AL). We found that ZD diet (0.2 p.p.m.) impaired ADP-induced aggre gation of washed platelet after 4 and 8 weeks of diet. Thrombin-induce d aggregation was impaired in ZD rats and PF rats after 8 weeks. The t hrombin-induced mobilization of radiolabeled arachidonate preincorpora ted into platelet phospholipids was followed as well as the subsequent formation of labeled cyclooxygenase and lipoxygenase products. Stimul ated platelets of ZD rats exhibited a decreased production of cyclooxy genase and lipoxygenase products, particularly after 8 weeks of diet. Moreover, platelet thromboxane generation was decreased in the ZD grou p as studied using a radioimmunoassay after thrombin stimulation. In a ddition, we measured the total fatty acid compositions of platelet and plasma. As a whole, 20:5 (n - 3) and 22:5 (n - 3) fatty acids content were significantly increased in platelet lipids after 8 weeks. On the other hand, it is known that enrichment of these fatty acids through dietary studies, both in animal and human as well as in vitro incorpor ation in platelets, resulted in an inhibition of platelet function, Co nsequently, these changes in platelet membrane fatty acid composition may contribute to the impaired platelet aggregation observed in ZD rat s.